Determination of Phenolic Antioxidant DBPC and DBP Levels in Electrical Insulating Oil

Význam tématu

Ensuring proper levels of phenolic antioxidants, specifically DBPC and DBP, is critical to prevent oxidative degradation in electrical insulating oils used in transformers and related equipment. Regular monitoring helps maintain oil integrity, extend service life, and avoid costly failures.

Cíle a přehled studie

This study develops and validates FTIR spectroscopy methods based on ASTM D2668 and IEC 60666 standards for quantifying DBPC and DBP concentrations. It extends the measurable range up to 1.0 wt% DBPC and 0.8 wt% DBP and demonstrates on-site applicability using portable FTIR instruments.

Použitá instrumentace

• Agilent 5500 FTIR spectrometer
• Agilent 4500 portable FTIR spectrometer
• Agilent Cary 630 FTIR spectrometer
• TumblIR and DialPath transmission cells (pathlengths: 100 µm, 200 µm, 500 µm, 1000 µm)
• MicroLab software for data processing and threshold-based reporting

Použitá metodika

Calibration standards were prepared by dissolving known amounts of DBPC in uninhibited mineral oil (Base 20 and Base 76). For ASTM D2668, samples (0–1.0 wt% DBPC) were analyzed with 100 µm cells using 128 scans at 8 cm⁻¹ resolution. For IEC 60666, samples (0–0.8 wt% DBPC) were measured at 200–1000 µm pathlengths with 64 scans at 4 cm⁻¹. Measurements targeted the phenolic OH stretch region around 3650 cm⁻¹.

Hlavní výsledky a diskuse

Both methods produced highly linear calibration curves (R² ≥ 0.999) with excellent repeatability and reproducibility (variance ≤ 0.02 wt%), surpassing specified limits. The extended concentration range exceeds standard coverage. MicroLab’s color-coded results and threshold alerts simplify interpretation and decision making.

Přínosy a praktické využití metody

• Rapid, on-site analysis reduces turnaround time and external laboratory dependence.
• Extended measurement range covers both fresh and aged oils.
• Threshold-based color coding and recommendations facilitate prompt maintenance actions.

Budoucí trendy a možnosti využití

• Integration into automated monitoring systems for continuous asset health tracking.
• Extension to other additive classes and lubricant types.
• Advanced software analytics, including AI-driven anomaly detection.

Závěr

Agilent 5500, 4500, and Cary 630 FTIR methods aligned with ASTM D2668 and IEC 60666 deliver precise, reliable, and rapid quantification of DBPC and DBP in electrical insulating oils. The ability to perform on-site measurements with intuitive software support enhances maintenance strategies for high-value equipment.

Reference

• F. Higgins. Onsite additive depletion monitoring in turbine oils by FTIR spectroscopy; Agilent Technologies, publication number 5990-7801EN (2011).